Browsing by Subject "Contact angle"

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Comparison of models for numerical simulation of low salinity waterflood
(2021-08-12) Santra, Ritabrata; Sepehrnoori, Kamy, 1951-; Delshad, Mojdeh
Accurately modeling Low Salinity Water Injection (LSWI) is essential for reliable predictions of oil recovery which affects exploration project planning and investment decisions. During LSWI, we modify the ions present in water before injection into an oil reservoir which helps maintain reservoir pressure and recover more oil from the reservoir, as compared to untreated regular water injection. Thus, understanding the primary mechanism and their effect of improved oil recovery due to wettability alteration during LSWI, and accurately modeling it, is essential to reliably predict and maximize oil recovery. However, there are several proposed models for numerical simulation of this novel method of LSWI and there exists no comparison for choosing the best model for an accurate simulation study. This study uses two simulators: (1) coupled reservoir simulator with geochemistry capabilities, UTCOMP-IPhreeqc and (2) commercial simulator, CMG’s GEM. We compare three models for numerical simulation of LSWI: (1) calcite dissolution, (2) total ionic strength, and (3) Extended Derjaguin, Landau, Verwey, and Overbeek (EDLVO). Most importantly, we also perform comparisons at both field and core scale. We describe the modeling capabilities of the two simulators and perform literature review to summarize the proposed mechanisms and the theory behind existing models. Finally, we simulate on (1) a synthetic carbonate field case, (2) a sandstone coreflood from a published literature, and (3) another sandstone coreflood, each with distinct mineralogy and petrophysical properties, to compare the three models. Results show that only the EDLVO model implemented in UTCOMP-Iphreeqc was able to accurately model the wettability alteration by estimating the change in contact angle during LSWI for all cases. While predicted recoveries from some of the models were similar, further investigation into the results uncovered the shortcomings of the other two models which resulted in incorrect calculation of the interpolating parameter. We concluded that the EDLVO model in UTCOMP-IPhreeqc works for all minerology while the other two models are scale, mineralogy, and case dependent. In future, we aim to develop a screening guide to choose model depending on the case, for simulating LSWI in commercial simulators which lack some of the mechanistic modeling capabilities of UTCOMP-IPhreeqc.
Electrical control and enhancement of dropwise condensation
(2020-06-22) Wikramanayake, Enakshi Devinka; Bahadur, Vaibhav; Ezekoye, Ofodike; Shi , Li; Bonnecaze , Roger
Condensation of vapor typically occurs via the formation of condensate films on condensing surfaces; however, the liquid film imposes a substantial thermal resistance to heat transfer. Filmwise condensation heat transfer can be enhanced by 5-7X by condensing vapor as droplets, which roll-off the surface, thereby preventing buildup of a liquid film. Dropwise condensation heat transfer can be enhanced by the use of electrowetting (EW) to enhance coalescence, growth and shedding of condensed droplets. This dissertation includes several fundamental studies on EW-enhanced dropwise condensation. Experiments, analytical modeling and statistical modeling are used to gain a deeper understanding of droplet growth, coalescence and shedding under EW. Chapter 1 details the motivation for this study and the objectives of this dissertation. Chapter 2 includes a literature review of condensation, electrowetting and data science- based statistical methods. Chapter 3 presents a detailed experimental study of dropwise condensation of humid air under the influence of electrowetting fields. An analytical heat transfer model, which accounts for the presence of non-condensable gases, is used to predict the heat transfer benefits associated with electrowetting-assisted condensation. Chapter 4 presents a detailed analysis of electrowetting-induced coalescence dynamics of a distribution of water droplets. Statistical modeling-based algorithms are used to identify key electrowetting-related parameters that influence droplet coalescence; the influence of these parameters on coalescence is quantified. Chapter 5 studies droplet shedding dynamics under electrowetting and shows that an intermittent electric field can significantly increase condensation rates (as compared to a continuous electric field). A key finding is the almost complete removal of water from surfaces in very short durations (< 1 sec) is observed. It is also found that the extent and rate of water removal depends on the applied voltage and frequency of the AC EW waveform, respectively. Chapter 6 presents a novel approach and an experimentally validated model to analyze the oscillations of water droplets under the influence of AC electrowetting. Chapter 7 summarizes key conclusions and outlines suggestions for future work. Overall, the research reported in this dissertation has led to fundamental contributions in the areas of condensation and microfluidics. This multidisciplinary work has involved experiments, analytical modeling and statistical modeling. Results show that electrowetting fields influence all the phenomena important in dropwise condensation (growth, coalescence, shedding of droplets). Electrowetting is therefore a powerful tool to control and enhance condensation heat transfer. This research impacts applications in energy (steam condensation, refrigeration), water (atmospheric water harvesting, desalination) and infrastructure (self-cleaning).
Surfactant-aided wettability alteration in low-temperature low-salinity carbonate reservoirs
(2021-08-02) Almansouri, Mohammed A.; Mohanty, Kishore Kumar
Carbonate reservoirs tend to be oil-wet/mixed-wet and heterogeneous, which makes wettability alteration a key method for increasing oil recovery. Carbonate reservoirs are often fractured, especially with increased dolomitization. Changing wettability to a water-wet state aids water imbibition into the matrix, thereby sweeping bypassed oil. The objective of this study is to improve oil recovery in low-temperature dolomite reservoirs using low-salinity surfactant solutions. This work evaluates the potential of using surfactants in a low-temperature carbonate formation with a formation brine salinity of 10,887 ppm. The reservoir has a high dolomite concentration with a high density of fractures and an intermediate to oil-wet wettability. Brine composition was optimized using zeta potential and contact angle measurements. Surfactants were screened based on their aqueous stability under reservoir conditions and were further screened using contact angle experiments. Experiments of spontaneous imbibition upon exposure to surfactants on carbonate rocks have been conducted using various surfactant types and concentrations. Also, a coreflood was completed to evaluate recovery due to wettability alteration. Additionally, changing water salinity was performed to assess the impact on the wettability of carbonate surfaces. The effects of surfactant formulations and observations are discussed. Optimized surfactant formulations were found to increase oil recovery to up to 10.4% from conventional waterflooding